JPH10150237A - Excimer laser device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an excimer laser device which is capable of stably outputting laser energy, where a voltage applied to a pre-ionizing electrode is quickly built up, and the discharge timing of a pre-ionizing electrode can be easily changed. SOLUTION: An excimer laser device has such a structure that a voltage across a pre-ionizing capacitor 3 is applied to pre-ionizing electrodes 7a and 7b to make a discharge occur between them to pre-ionize laser gas when change accumulated in a primary capacitor 2 is transferred to a secondary capacitor 5 through the intermediary of a switching device 4 to enable a primary discharge to occur between primary discharge electrodes 5a and 5b to excite laser gas, wherein a magnetic switch 10 is connected between the pre-ionizing capacitor 3 and the pre-ionizing electrodes 7a and 7b, a switching device 4 is made completely conductive in a retention time set by the magnetic switch 10, and then the magnetic switch 10 is turned on to apply a voltage across the pre- ionizing capacitor 3 to the pre-ionizing electrodes 7a and 7b.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a discharge excitation type excimer laser device.

[0002]

2. Description of the Related Art An excimer laser apparatus uses a rare gas (Ar,
An ultraviolet pulse laser (excimer laser) is oscillated by exciting the laser gas by discharging in a mixed gas (laser gas) of a halogen gas (F, Cl, etc.) and a halogen gas (F, Cl, etc.). Therefore, in the laser tube, a pair of main discharge electrodes that generate a main discharge to excite the laser gas, and a main discharge seed called preionization before the main discharge to obtain a uniform main discharge effective for excitation A pre-ionization electrode is provided for generating a pre-ionization discharge prior to the main electron discharge, and weakly ionizing the laser gas between the main discharge electrodes by ultraviolet light generated from the pre-ionization discharge.

FIG. 3 shows an example of a laser gas excitation circuit in such an excimer laser apparatus. In this figure, 1 is a high-voltage power supply input terminal, 2 is a primary capacitor, 3 is a preionization capacitor, and 4 is Switching elements such as thyratrons, 5 is a secondary capacitor, 6a and 6b are a pair of main discharge electrodes, 7a and 7b are preliminary ionization electrodes, 8a and
8b is a dielectric, L1 and L2 are charging inductances, L
3, L4 is a circuit inductance. The preionization electrodes 7a and 7b of this example are disposed inside the dielectrics 8a and 8b, respectively, and a high voltage is applied to the preionization electrodes 7a and 7b to generate a high electric field on the surfaces of the external dielectrics 8a and 8b, thereby generating corona discharge. Have been caused to occur.

[0004] The laser gas excitation circuit having the above-described configuration is configured such that when the switching element 4 is turned off, a high-voltage power supply (not shown) connected to the high-voltage power supply input terminal 1 supplies the primary capacitor 2 and the preionization capacitor 3 respectively. It is charged via the charging inductances L1 and L2. When the switching element 4 is turned on, the electric charge charged in the primary capacitor 2 moves to the secondary capacitor 5.

When the voltage of the secondary capacitor 5 reaches a predetermined high voltage due to this transition, a glow discharge occurs between the main discharge electrodes 6a and 6b, and the discharge excites a laser gas to output a laser beam. On the other hand, when the switching element 4 is turned on, the voltage of the pre-ionization capacitor 3 is applied to the pre-ionization electrodes 7a and 7b, and this voltage causes a corona discharge on the surfaces of the dielectrics 8a and 8b. The irradiated ultraviolet light is applied to the laser gas between the main discharge electrodes 6a and 6b to perform preliminary ionization of the laser gas before the main discharge.

The pre-ionization method using corona discharge does not cause consumption of the pin array due to power discharge sputtering or contamination of laser gas as compared with the arc pre-ionization method in which arc discharge is performed between a plurality of pin arrays to perform pre-ionization. , Laser equipment and laser gas life can be extended,
On the other hand, compared with the arc preionization method, the amount of emitted ultraviolet light is small and the preionization effect is inferior.

[0007]

In the conventional laser gas excitation circuit as described above, the switching element 4
Is turned on, the voltage of the preionization capacitor 3 is applied to the preionization electrodes 7a and 7b. In this case, when the switching element 4 is turned on, the voltage of the preionization capacitor 3 is instantaneously changed to the preionization electrode. Rather than being applied to the electrodes 7a and 7b, the switching element 4 has a time required for turning on (the time from when a trigger is applied to the switching element 4 until the impedance of the switching element 4 is sufficiently reduced). Therefore, the rise of the voltage applied to the preliminary ionization electrodes 7a and 7b is slow, and the amount of radiation ultraviolet light for performing the preliminary ionization is small accordingly (the rise of the voltage applied to the preliminary ionization electrode, that is, the rate of change of the voltage is small) The larger the size, the larger the amount of emitted ultraviolet light). Further, there is a problem that the timing of the preionization discharge cannot be controlled and cannot be optimized.

SUMMARY OF THE INVENTION The present invention has been made in view of the above-mentioned problems, and enables a rapid rise of the voltage applied to the preionization electrode and easy change of the timing of the preionization discharge, thereby obtaining a stable laser output energy. It is an object of the present invention to provide an excimer laser device that can be used.

[0009]

SUMMARY OF THE INVENTION The object of the present invention is to provide a primary capacitor charged by a high voltage power supply, a switching element which is turned on at a predetermined timing, and the primary capacitor which is turned on when the switching element is driven. , A main discharge electrode that discharges by charging the secondary capacitor to excite a laser gas, a preionization capacitor that is charged by a high-voltage power supply, and the preionization when the switching element is turned on. An excimer laser comprising: a pre-ionization electrode to which a voltage of a pre-ionization capacitor is applied to pre-ionize the laser gas; and a magnetic switch inserted and connected between the pre-ionization capacitor and the pre-ionization electrode. This is achieved by using a device.

According to the above feature of the present invention, the voltage of the pre-ionization capacitor is held by the magnetic switch for the time required for turning on the switching element when the switching element is turned on, and then turned on by the magnetic switch. Since the voltage is applied to the preionization electrode almost instantaneously, the rise of the voltage applied to the preionization electrode is fast, thereby increasing the amount of emitted ultraviolet light for preionization. Further, by changing the holding time of the magnetic switch, the timing of the preionization discharge with respect to the main discharge can be controlled, and the preionization discharge can be optimized.

[0011]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a laser gas excitation circuit diagram of an example of the excimer laser device according to the present invention, and FIG. 2 is a laser gas excitation circuit diagram of another example of the excimer laser device according to the present invention. In each figure, the same portions as those shown in FIG. 3 are denoted by the same reference numerals, and the description of the overlapping portions will be omitted.

According to the present invention, a magnetic switch 10 is inserted and connected between the preionization capacitor 3 and the preionization electrodes 7a and 7b of the laser gas excitation circuit. The laser gas excitation circuit shown in FIG. 1 is connected to a high-voltage power supply (not shown) connected to a high-voltage power supply input terminal 1 when a switching element 4 is turned off to a primary capacitor 2 and a pre-ionization capacitor 3, respectively, as in the prior art. It is charged via the charging inductances L1 and L2. When the switching element 4 is turned on, the electric charge charged in the primary capacitor 2 shifts to the secondary capacitor 5. When the shift causes the voltage of the secondary capacitor 5 to reach a predetermined high voltage, the main discharge electrode Glow discharge occurs between 6a and 6b, and laser oscillation is performed.

On the other hand, when the switching element 4 is turned on, the voltage of the pre-ionization capacitor 3 becomes
After a certain holding time by 0 has elapsed, the magnetic switch 10 is turned on and applied to the preliminary ionization electrodes 7a and 7b at the latest just before the laser oscillation. This voltage causes the dielectric 8
Corona discharge is generated on the surfaces of a and 8b, and the ultraviolet light generated by the corona discharge is applied to the laser gas between the main discharge electrodes 6a and 6b to perform preliminary ionization of the laser gas.

At the time when the magnetic switch 10 is turned on, the impedance of the switching element 4 is sufficiently lower than the transition of the capacity of the main discharge circuit, so that the voltage applied to the preliminary ionization electrodes 7a and 7b due to the rise of the switching element 4 The rising dullness of is avoided. In this case, the magnetic switch 10 also has a rise time required to turn on, but is sufficiently shorter than the rise time of the switching element 4 (normally, the rise time of the thyratron of the switching element 4 used is 40 to 50 nS. And the magnetic switch 10 is 20 ns or less.)
The rise of the voltage to a and 7b is accelerated. Further, by selecting the holding time of the magnetic switch 10, it is possible to easily control the timing of the preionization discharge with respect to the main discharge.

The magnetic material used for such a magnetic switch 10 is an Fe-based amorphous alloy, a Co-based amorphous alloy, a ferrite, or the like, but an amorphous alloy capable of sharply rising and sharp switching is preferable.

By the way, in the laser gas excitation circuit, FIG.
As shown in FIG. 5, a magnetic switch 11 called a magnetic assist is connected in series with the switching element 4 for the purpose of protecting the switching element 4 and reducing power loss. In some cases, the magnetic switch 11 may prevent the current from flowing into the switching element 4 by the magnetic switch 11 for a fixed holding time (for a short time) so that the current does not flow.

In such a laser gas excitation circuit as well, the pre-ionization capacitor 3 and the pre-ionization electrodes 7a, 7b
By inserting the magnetic switch 10 between them, the same operation and effect as those of the laser gas excitation circuit of FIG. 1 can be obtained. However, in this case, the holding time of the magnetic switch 10 needs to be longer than the holding time of the magnetic switch 11.

In the above embodiment, the preionization method using the creeping corona discharge is used. However, the preionization method using other discharge forms, for example, a discharge using a space corona discharge, a pulse streamer discharge, a silent discharge, and an arc discharge. The system may be used.

[0019]

As described in detail above, according to the present invention,
After turning on the switching element that performs the capacitance transfer, the switching element is completely turned on by the capacitance transfer during the holding time by the magnetic switch, and then the magnetic switch is turned on and the voltage of the preionization capacitor is applied to the preionization electrode. Since the voltage is applied, the voltage applied to the preionization electrode rises quickly, the amount of emitted ultraviolet light for preionization increases, and the timing of the preionization discharge with respect to the main discharge can be optimally set. As a result, the excitation discharge becomes uniform, and the stability of laser output energy and pulse energy can be obtained.

[Brief description of the drawings]

FIG. 1 is a laser gas excitation circuit diagram of an example of an excimer laser device according to the present invention.

FIG. 2 is a laser gas excitation circuit diagram of another example of the excimer laser device according to the present invention.

FIG. 3 is a laser gas excitation circuit diagram of an example of a conventional excimer laser device.

[Description of Signs] 2 Primary capacitor 3 Pre-ionization capacitor 4 Switching element 5 Secondary capacitor 6a, 6b A pair of main discharge electrodes 7a, 7b Pre-ionization electrode 8a, 8b Dielectric 10, 11 Magnetic switch

Claims (1)

[Claims] A primary capacitor charged by a high-voltage power supply; a switching element that is turned on at a predetermined timing; a secondary capacitor that is charged by the primary capacitor when the switching element is turned on; A main discharge electrode that discharges to excite the laser gas by charging the next capacitor; a pre-ionization capacitor charged by a high-voltage power supply; and a voltage of the pre-ionization capacitor is applied when the switching element is driven to turn on the laser gas. An excimer laser device comprising: a preionization electrode for ionization; and a magnetic switch inserted and connected between the preionization capacitor and the preionization electrode.